While the 40-yard dash might be the most important drill for many of the NFL prospects who will gather at the NFL Scouting Combine beginning next week, it won't be the pivotal test for former Missouri defensive end Michael Sam, the NFL's first openly gay draft prospect.

"Hip flip is the most important thing for Michael Sam to show at the NFL Combine," Gaines said, "because the bottom line is this, if you can't turn and run, you can't play in the NFL."

The hip flip drill requires athletes to backpedal, then turn and sprint, to show NFL scouts their flexibility in coverage. Sam (6-foot-1, 255 pounds) is undersized to stay at the defensive end position, where he amassed 11.5 sacks and 19 tackles for loss as a senior at Missouri. As such, he'll likely have to make the switch to linebacker, which requires an entirely different skill set.

Along with the hip flip drill, Gaines said Sam will also be challenged to show change-of-direction skills, crucial for playing in pass coverage, but not something he required much of as a pass rusher in college.

"For Michael, he has to have a very great W drill," Gaines said, referring to a drill in which players are timed changing directions from forward to backward, and forward again. The box drill will be similarly important for Sam, Gaines said. The box drill tests prospects' ability to change direction and move laterally, as well, unlike the W drill.

"The box drill is important because he shows he has a great burst going forward, and also can change directions quickly, so he can cover those shifty running backs coming out of the backfield in the NFL," Gaines said.

Sam has been projected as a third- to fifth-round draft pick in May by some analysts, although those projections are among the most favorable. At least one NFL general manager believes he is overrated and won't be drafted at all. NFL Media senior analyst Gil Brandt has expressed some concerns about Sam's NFL potential, as well:

Michael Sam was not in my top 100 sr #NFL prospects. Player w/out position. Can't play in space, not big enough to play w hand on ground